FIG. 1 is an LED cassette unit 200 which is disclosed in U.S. Pat. No. 7,445,355. The LED cassette unit 200 has a top metal electrode 21 and a bottom metal electrode 22. An insulation layer 25 is sandwiched in between the top metal electrode 21 and the bottom metal electrode 22. A center void is made in a center of the top metal electrode 21 and the insulation layer 25 to expose a center surface of the bottom metal electrode 22. An LED 20 is mounted on the bottom metal electrode 22 in the center void. A metal wire 24 electrically couples a top electrode of the LED 20 to the top metal electrode 21. A bottom electrode of the LED 20 electrically contacts the bottom metal electrode 22. Protection glue 23 encapsulates the metal wire 24 and the LED 20 for ensuring the quality and reliability of the LED package.